1. Field of the Invention
The invention relates to a self-emissive display device and in particular to an organic light-emitting device (OLED) with a micro-cavity structure.
2. Description of the Related Art
Organic light-emitting diodes (OLEDs) are active lighting devices using organic materials. Compared with conventional inorganic LEDs, OLEDs can be easily fabricated on a large substrate by forming an amorphous silicon layer thereon. Additionally, displays utilizing OLEDs require no backlight module, such that the manufacturing process is simpler and relatively lower in costs. OLED technology is highly developed and can be employed in small panels such as those in personal digital assistants (PDAs) or digital cameras. As OLED technology matures, applications in larger panels such as personal computers, televisions and even flexible displays will be possible.
A typical OLED may comprise an anode, a cathode and an organic electroluminescent layer disposed between the anode and the cathode. The anode and the cathode are oppositely disposed on a substrate. The organic electroluminescent layer comprises a hole injection layer (HIL) and a hole transport layer (HTL) adjacent to the anode, an electron injection layer (EIL) and an electron transport layer (ETL) adjacent to the cathode 214, and an emitting material layer (EML) sandwiched between the HTL and the ETL. When an electrical potential difference is applied between the cathode and the anode, electrons are injected into the ETL from the cathode through the EIL, and then pass through the ETL and the EML. At the same time, holes are injected into the HTL from the anode through the HIL, and then pass therethrough. The injected electrons and holes are recombined at the interface of the EML and the HTL, releasing energy as light.
An organic electroluminescent layer may be placed within a micro-cavity structure to improve efficiency and color saturation of the OLED. In the micro-cavity structure, the emitting light may induce constructive and destructive interferences to enhance emission at a specific wavelength. However, the light intensity and wavelength may be varied when viewed at various angles, such that the view angle is reduced. In other words, in the OLED with a micro-cavity structure, the color of the emission may be changed (i.e. color shift) when viewed at various angles.
Thus, there exists a need for an improved OLED capable of increasing efficiency and color saturation while mitigating the color shift problem.